FR2301596A1 - Oxygen refining pig iron - with half the normal melt height to improve dephosphorisation - Google Patents

Abstract

In an O2 refining process for producing steel, in which O2 is infected together with a cooling agent such as a liq. or gaseous hydrocarbon, low P contents can be obtd. without reducing the C content to too low a level by reducing the height of the pig-iron melt above the O2 nozzles according to H >= Ho/2 1 + (Q-Qo/Qo) 1/2 where H is the height of the melt (in cm) corresponding to the O2 flow desired Q (in m3/min) and Ho is the usual height of the melt in normal practice corresponding to an O2 flow Qo so that a liq. slag esp. a dephosphorising slag is formed. The slag is formed early in the O2-refining operation and dephosphorisation is improved thus allowing high P contg. ores to be used. Since the C content is not too low the melt is not excessively oxidised. By reducing the height of the melt the effect is similar to that obtd. by increasing the rate of blowing or the dia. of each tuyere without the complications which arise from using these latter two methods. Thermal savings are made since the CO at the surface is burnt to produce CO2, steam is exothermically formed from the H2 evolved, and the O2 spends less time in the melt and therefore removes less heat. The higher temps. produced are also favourable to the formation of the slag. The increased temp. at the surface leads to greater dissolution of the limestone and inhibits foaming of the SiO2 slag which would greatly increase the apparent volume of the melt.